Extraction of filaments from a liquid melt has been employed to form amorphous metal filaments. For example, Bedell et al., in U.S. Pat. No. 3,863,700, disclose a method and apparatus for filament extraction from molten metal contained in a vessel. The Bedell et al. patent offers no teaching which overcomes the problem of reaction of the melt with the vessel containing the melt when either a high melting or a reactive material is employed. Alloys containing large concentrations of titanium, zirconium, niobium, vanadium, chromium, and the like, when molten are known to react with refractory crucible materials such as alumina, fused silica, zirconia, thoria, yttria, beryllia, and the like. Reaction with the crucible can cause: contamination of the melt which can result in embrittlement of the cast filament; formation of insoluble inclusions in the melt which can reduce the fluidity of the melt, and thereby change its casting characteristics; and attack of the crucible by the melt which will shorten the life of the crucible.
By the appropriate selection of the crucible material employed with a particular alloy, the above-mentioned problems can be minimized but not eliminated. The selection process may require extensive experimentation to determine the compatible combinations of alloy and crucible material. In many cases the crucible material that is subject to minimal attack by the alloy may suffer from thermal instability and be subject to cracking when thermally cycled.
High temperature nickel-base, nickel-chromium-titanium-aluminum alloys have been melted in water-cooled copper crucibles. British Pat. No. 1,517,283, teaches the use of a water-cooled crucible to contain nickel-based alloys. The melt is removed from the crucible by spinning the crucible about its axis to generate atomized particles of liquid which move out radially from the edge of the crucible. This patent offers no teaching that the melt can be extracted from the crucible in the form of a continuous stream of limited dimensions.
Likewise, British Pat. No. 1,428,691 teaches that alloys can be melted in water-cooled molds. The melt is then solidified in situ. This patent offers no teaching of a technique for the extraction of liquid metal from a water-cooled mold.
Since the electrodes used to supply heat to the melts in the above patents are directly above the melt, it is necessary to form a stream of controlled dimensions away from these electrodes if a filament of metal is to be extracted. Thus, while the above patents show a method for melting materials in water-cooled crucibles, they provide no teachings which are suitable for extraction of filaments from the liquid melt.